Li Zeng-quan, Jiang Chang-sheng, Hao Qing-ju
Huan Jing Ke Xue. 2015 Nov;36(11):4241-51.
In this study, four land use types including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land were selected to collect soil samples from 0 to 60 cm depth at the same altitude in Jinyun Mountain. Four sizes of large macroaggregates (> 2 mm), small macroaggregates (0.25-2 mm), microaggregates (0.053-0.25 mm) and silt + clay (< 0.053 mm) were achieved by wet sieving method and the contents of microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) in each aggregate fraction were measured to study the impacts of the different land use types on MBC and MBN in soil aggregates. The results showed that the contents of MBC and MBN in all aggregates in the four land use types decreased with the increasing soil depth. Except large macroaggregetes, the contents of MBC and MBN in the other three soil aggregates decreased when the forest was reclamated into orchard and sloping farmland. MBC and MBN contents in large macroaggregates, small macroaggregates and microaggregates all increased when the sloping farmland was abandoned. The storages of organic carbon and nitrogen in soil depth of 0-60 cm in the four proportions were calculated by the equivalent soil mass method. The results revealed that MBC storages in the other three sizes except silt + clay were higher in the forest than those in orchard and sloping land. And MBC storages in the all aggregates were higher in the abandoned land than those in the sloping land. MBN storages in small macroaggregates and microaggregates were higher in the forest than those in orchard and sloping land. And MBN storages in the other three aggregates except silt + clay were higher in the abandoned land than those in the sloping land. Generally speaking, the storages of MBC in soil aggregates of forest and abandoned land were higher than in orchard and sloping land, MBN storage in soil aggregates of forest was nearly equal to the storage in orchard. However, the storages of MBN in soil aggregates of forest and abandoned land were higher than those in sloping land. The results showed that the reclamation of the forest resulted in the loss of MBC and MBN in soil aggregates of sloping land. However, the abandon of the sloping land contributed to the acumulation of MBC and MBN in soil aggregates. In the process of land use change, the direction and quantity of change in MBC in the soil aggregates were not consistent with those of the total soil organic carbon, which meant the microbial quotient in soil aggregates was not suitable for using to evaluate the impact of land use change on soil quality, using the total organic carbon as an index to express the sensitivity of the land use change may be better.
本研究选取了亚热带常绿阔叶林（简称：森林）、坡耕地、果园和荒地4种土地利用类型，在缙云山同一海拔高度采集0至60厘米深度的土壤样本。通过湿筛法得到了4种粒径的大团聚体（>2毫米）、小团聚体（0.25 - 2毫米）、微团聚体（0.053 - 0.25毫米）和粉粒 + 黏粒（<0.053毫米），并测定了各团聚体组分中微生物量碳（MBC）和微生物量氮（MBN）的含量，以研究不同土地利用类型对土壤团聚体中MBC和MBN的影响。结果表明，4种土地利用类型中所有团聚体的MBC和MBN含量均随土壤深度增加而降低。除大团聚体外，森林开垦为果园和坡耕地时，其他3种土壤团聚体的MBC和MBN含量均降低。坡耕地撂荒后，大团聚体、小团聚体和微团聚体中的MBC和MBN含量均增加。采用等效土壤质量法计算了4种粒径在0至60厘米土壤深度中的有机碳和氮储量。结果表明，除粉粒 + 黏粒外，森林中其他3种粒径的MBC储量均高于果园和坡耕地。撂荒地所有团聚体的MBC储量均高于坡耕地。森林中小团聚体和微团聚体的MBN储量高于果园和坡耕地。除粉粒 + 黏粒外，撂荒地其他3种团聚体的MBN储量高于坡耕地。总体而言，森林和撂荒地土壤团聚体中的MBC储量高于果园和坡耕地，森林土壤团聚体中的MBN储量与果园相近。然而，森林和撂荒地土壤团聚体中的MBN储量高于坡耕地。结果表明，森林开垦导致坡耕地土壤团聚体中MBC和MBN损失。然而，坡耕地撂荒有助于土壤团聚体中MBC和MBN的积累。在土地利用变化过程中，土壤团聚体中MBC的变化方向和数量与土壤总有机碳不一致，这意味着土壤团聚体中的微生物商不适合用于评估土地利用变化对土壤质量的影响，以总有机碳为指标来表达土地利用变化的敏感性可能更好。
